The research effort of this program continues to focus on specific objectives relevant to an understanding of the relationship between 1. estrogen carcinogenesis and the steroid hormone receptor system in the hamster kidney, 2. interaction of steroid hormones in tumor dependency, 3. the relationship between partial steroid hormone responsiveness and tumor growth in partially autonomous renal tumor variants, 4. steroid hormone receptor profiles in human renal cell cancer. The estrogen induced and dependent renal carcinoma provides a unique system to study the hormonal interrelationships involved in tumor response to endocrine therapy as well as the interaction of all steroid hormones within a single tissue. This model is useful in elucidating the mechanisms of hormone dependence and responsiveness in such human carcinomas as cancer of the breast, endometrium, and prostate in which hormone responsiveness and/or specific hormone receptors are established clinical findings. Specifically, the induction of progesterone receptor in the hamster kidney as a result of estrogen treatment and its subsequent modulation by antiestrogens, and progestins corresponds or may be understood in the inhibition of estrogen renal tumorigenesis. The relationship between these responses and estrogen carcinogenesis needs clarification. Secondly, the effect of steroid hormones, administered individually and in combination and various antihormones, on RNA and protein synthesis will initially be studied in minced tumor preparations and hopefully later in either cell suspension or in cell culture to make more precise determinations. Thirdly, further characterization of the steroid hormone receptors will be carried out using partially purified receptor preparations. The partially purified receptor will be useful in determining the nature of competition by antiestrogens and binding to acceptor chromosomal proteins.